refactor: use TypeSignature::Coercible for crypto functions

[Chen-Yuan-Lai]

Which issue does this PR close?

• Closes TypeSignature::Coercible for crypto functions #14762 .

Rationale for this change

What changes are included in this PR?

Are these changes tested?

Are there any user-facing changes?

[Chen-Yuan-Lai]

Hi @jayzhan211, I encountered some CI failures in the digest function. It seems the Exact(vec![Utf8View, Utf8View]) case can't be replaced with TypeSignature::Coercible because TypeSignature::Coercible processes each parameter independently, without considering the types of other parameters

[SQL] EXPLAIN SELECT
  digest(column1_utf8view, 'md5') as c
FROM test;
[Diff] (-expected|+actual)
    logical_plan
-   01)Projection: digest(test.column1_utf8view, Utf8View("md5")) AS c
+   01)Projection: digest(test.column1_utf8view, Utf8("md5")) AS c
    02)--TableScan: test projection=[column1_utf8view]

Should we:

1. Implement a new TypeSignature::Coercible method to support this feature?
2. Mixing the usage TypeSignature::Coercible and Exact(vec![Utf8View, Utf8View]) in digest function?

I'm not sure which one is better, could you give me some suggestions or other best practices? thanks very much!!